1. Field of the Invention
The present invention relates to a medical prosthesis for human implantation, and in particular, to an artificial blood vessel which is utilized to replace damaged blood vessels, or as a device for bypassing blood vessels.
2. Description of the Prior Art
Vascular diseases have become one of the most important diseases that threaten human health and life. An important method for treating vascular diseases is to use an artificial blood vessel to replace the diseased blood vessel, or to bypass the diseased portion of the vessel. Currently, the most commonly-used artificial blood vessels for clinical application are knitted Dacron tubes or expanded polytetrafluoroethylene tubes, both being produced from synthetic materials which can be used to form internal pseudomembranes and to maintain long-term smooth passage of blood. Unfortunately, all foreign matters that are implanted into a human body face some degree of chronic rejection sooner or later, which can lead to an adverse reaction in the body. In addition, the anticoagulation of these conventional artificial blood vessels is poor, and usually only artificial blood vessels having a diameter of at least a 6 mm provide good passage, so that smaller-diameter artificial blood vessels, especially those having diameters of less than 4 mm, often result in embolisms after being implanted.
There have been many studies using animal blood vessels as artificial blood vessels for humans, but none have become a viable product for clinical application because the techniques for treatment are out-of-date. For example, the conventional treatment methods include fixing an animal blood vessel with glutaraldehyde, followed by defatting and cell removal, and then the product is directly implanted. Treatment with glutaraldehyde is for fixing the protein molecules in the animal tissue through crosslinking by the acetal reaction, but toxic glutaraldehyde is slowly released due to degradation after the animal blood vessel treated in this manner is implanted into a human body, thereby inhibiting the production of endothelial cells in the blood vessel. In addition, the conventional treatment method employs cell removal as an effective means for eliminating or removing antigens, but according to research results in molecular biology and molecular immunology, antigenicity does not only originate from the cell, but also from active groups at certain specific locations on the proteins and polysaccharides, or specific conformations. These specific groups or conformations are called antigenic determinants clusters, and antigens can only be eliminated by blocking the active groups of the antigenic determinants and altering the specific conformation of the antigenic determinants; antigens cannot be effectively eliminated by cell removal.
Accordingly, the conventional methods for treating animal blood vessels do not totally eradicate chronic immune rejection due to the toxic presence of residual glutaraldehyde and the incomplete elimination of the antigens, making it very difficult for the endothelial cells and other vascular cells of the host blood vessels to migrate and grow into the artificial blood vessel, so that the expected effects cannot be attained.